Process for producing blends of syndiotactic, 1,2-polybutadiene and rubbery elastomers

ABSTRACT

Blends of syndiotactic 1,2-polybutadiene and rubbery elastomers are prepared by a process that comprises polymerizing 1,3-butadiene monomer into syndiotactic 1,2-polybutadiene within a rubber cement of an elastomeric terpolymer by using a chromium-based, molybdenum-based, or iron-based catalyst composition. Polymer composition comprising the blend with improved properties is also provided.

[0001] This application is a continuation-in-part of internationalapplication PCT/US02/35402, which claims priority from U.S. ProvisionalPatent Application No. 60/338,840 filed on Nov. 5, 2001, which areincorporated herein by reference.

BACKGROUND

[0002] The present invention is directed toward a process for producingblends of syndiotactic 1,2-polybutadiene and rubbery elastomers. Thepresent invention is also directed to a polymer composition comprising ablend of syndiotactic 1,2-polybutadiene and a terpolymer polymerizedfrom ethylene, at least one α-olefin monomer, and at least one dienemonomer.

[0003] Tire sidewalls protect the ply and are therefore preferablyresistant to weathering, ozone, abrasion, and tearing, while providingexcellent flex fatigue resistance. Typical tire sidewall formulationsinclude natural rubber (NR), styrene-butadiene (SBR), butadiene (BR),and halogenated butyl (HIIR). Ethylene-propylene-diene terpolymer (EPDM)is attractive because of its resistance to weathering and ozone.

[0004] EPDM, however, is not compatible with butadiene rubber andfillers, and has poor cut growth resistance. Blends of EPDM withcrystalline polymers have shown improved cut growth properties at roomtemperature. At elevated temperatures, however, these materials havepoor cut growth properties.

[0005] Syndiotactic 1,2-polybutadiene (sPB) is a crystallinethermoplastic resin that has a stereoregular structure in which theside-chain vinyl groups are located alternately on the opposite sides inrelation to the polymeric main chain. sPB uniquely exhibits theproperties of both plastics and rubber, and therefore it has many uses.It can also be blended into and co cured with natural and syntheticrubbers.

[0006] Syndiotactic 1,2-polybutadiene can be made by solution, emulsion,or suspension polymerization. Generally, syndiotactic 1,2-polybutadienehas a melting temperature within the range of about 195° C. to about215° C., but due to processability considerations, it is generallydesirable for syndiotactic 1,2 polybutadiene to have a meltingtemperature of less than about 195° C.

[0007] Because syndiotactic 1,2-polybutadiene is insoluble in commonsolvents at normal polymerization temperatures, a common technicaldifficulty in the synthesis of syndiotactic 1,2-polybutadiene is thatthe polymerization mixture is an extremely thick slurry at thecommercially desirable polymer concentration of 10% to 25% by weight.This thick slurry becomes difficult to stir and transfer, therebydiminishing heat transfer efficiency and interfering with proper processcontrol. Also, the slurry contributes to reactorfouling due to theundesirable build-up of insoluble polymer on the baffles, agitatorblades, agitator shafts, and walls of the polymerization reactor. It istherefore necessary to dean the reactor on a regular basis, whichresults in frequent shutdowns of continuous processes and seriouslimitations of the run length of batch processes. The task of cleaningthe fouled reactor is generally difficult and time-consuming. All ofthese drawbacks detrimentally affect productivity and the cost ofoperation.

[0008] The physical properties of rubbery elastomers can be improved byblending crystalline polymers therein. For example, incorporatingsyndiotactic 1,2-polybutadiene into rubber compositions that areutilized in the supporting carcass of tires greatly improves the greenstrength of those compositions. Also, incorporating syndiotactic1,2-polybutadiene into tire tread compositions can reduce heat build-upand improve wear characteristics of tires. The green strength ofsynthetic rubbers such as cis-1,4-polybutadiene can also be improved byincorporating a small amount of syndiotactic 1,2-polybutadiene.

[0009] Blends of crystalline polymers and rubbery elastomers aretypically prepared by standard mixing techniques. For example, theseblends can be prepared by mixing or kneading and heat-treating acrystalline polymer and a rubbery elastomer by utilizing generally knownmixing equipment such as a Banbury mixer, a Brabender mixer, anextruder, a kneader, or a mill mixer. These high-temperature mixingprocedures, however, have certain drawbacks including high processingcosts, polymer degradation and crosslinking, inadequate mixing, as wellas various process limitations. Due to the high vinyl content ofsyndiotactic 1,2-polybutadiene, polymer degradation and crosslinking isa particularly severe problem for mixing syndiotactic 1,2-polybutadienewith elastomers at high temperatures.

[0010] Attempts to polymerize 1,3-butadiene into syndiotactic1,2-polybutadiene within a rubber cement have been hampered by catalystinefficiendes and toxicities. For example, U.S. Pat. No. 4,379,889teaches polymerizing 1,3-butadiene into syndiotactic 1,2-polybutadienewithin a rubber cement by using a catalyst system comprising a cobaltcompound, a dialkylaluminum halide, carbon disulfide, and an electrondonative compound. And, U.S. Pat. No. 5,283,294 teaches a similarprocess that employs a catalyst system comprising a cobalt compound, anorganoaluminum compound, and carbon disulfide. These methods, however,are inferior because the catalyst systems that are employed suffer fromlow catalytic activity, poor stereoselectivity, the need for toxic,halogenated solvents, and the many drawbacks associated with carbondisulfide including low flash point, obnoxious smell, high volatilityand toxicity.

[0011] Therefore, it would be advantageous to develop a new andsignificantly improved process for producing blends of syndiotactic1,2-polybutadiene and rubbery elastomers.

SUMMARY OF THE INVENTION

[0012] In general, the present invention provides a process forpreparing blends of syndiotactic 1,2-polybutadiene and rubberyelastomers comprising the steps of (1) providing a mixture of a rubbercement and 1,3-butadiene monomer; and (2) polymerizing the 1,3-butadieneinto syndiotactic 1,2-polybutadiene within the rubber cement by using acatalyst composition that is formed by combining, (a) achromium-containing compound, (b) a hydrogen phosphite, and (c) anorganomagnesium compound or (a) a molybdenum-containing compound or aniron-containing compound, (b) a hydrogen phosphite, and (c) anorganoaluminum compound.

[0013] The present invention further provides a process for preparingblends of syndiotactic 1,2-polybutadiene and rubbery elastomerscomprising the steps of (1) providing a mixture of a rubber cement and1,3-butadiene monomer, where the rubber cement comprises an elastomericterpolymer polymerized from ethylene, at least one-olefin monomer, andat least one diene monomer; and (2) preparing a catalyst composition,where the catalyst composition is prepared by combining, outside thepresence of the mixture of rubber cement and monomer, (a) achromium-containing compound, (b) a hydrogen phosphite, and (c) anorganomagnesium compound or (a) a molybdenum-containing compound or aniron-containing compound, (b) a hydrogen phosphite, and (c) anorganoaluminum compound; and (3) adding the catalyst composition to themixture and thereby polymerizing the 1,3-butadiene monomer intosyndiotactic l 1,2-polybutadiene within the rubber cement.

[0014] Advantageously, the process of this invention directly providesblends of syndiotactic 1,2-polybutadiene and rubbery elastomers bysynthesizing syndiotactic 1,2-polybutadiene within a rubber cement andthereby obviates the need for high-temperature mixing. Also, gooddispersion of syndiotactic 1,2-polybutadiene throughout rubberyelastomers can be easily and economically achieved. Significantly, theprocess of this invention eliminates the problems of high processingcosts, polymer degradation and crosslinking, inadequate mixing, andvarious process limitations that are associated with high-temperaturemixing procedures. The process of this invention also alleviates theproblems of polymer cement thickness and reactor fouling that areassociated with the synthesis of syndiotactic 1,2-polybutadiene in theabsence of a rubbery elastomer.

[0015] In addition, the catalyst systems employed in this invention havevery high catalytic activity and stereoselectivity for thesyndiospecific polymerization of 1,3-butadiene. This activity andselectivity, among other advantages, allows syndiotactic1,2-polybutadiene to be produced in very high yields within a rubbercement. Additionally, these catalyst compositions do not contain carbondisulfide, and therefore the toxicity, objectionable smell, dangers, andexpense associated with the use of carbon disulfide are eliminated.Further, the chromium, molybdenum, and iron compounds are generallystable, inexpensive, relatively innocuous, and readily available.Furthermore, these catalyst compositions have high catalytic activity ina wide variety of solvents including the environmentally preferrednonhalogenated solvents such as aliphatic and cydoaliphatichydrocarbons.

[0016] Furthermore, blends of syndiotactic 1,2-polybutadiene andelastomeric terpolymers polymerized from ethylene, at least one α-olefinmonomer, and at least one diene monomer, prepared by the process of thepresent invention, exhibit improved cut growth resistance at elevatedtemperatures.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0017] The present invention is generally directed toward a process forproducing blends of syndiotactic 1,2-polybutadiene and rubberyelastomers. Blends of syndiotactic 1,2-polybutadiene and rubberyelastomers can be directly produced by polymerizing 1,3-butadienemonomer into syndiotactic 1,2 polybutadiene within a rubber cement byusing chromium-based, molybdenum-based, or iron-based catalystcompositions.

[0018] The process includes the steps of: (1) providing a mixture of arubber cement and 1,3-butadiene monomer, where the rubber cementincludes at least one rubbery elastomer within an organic solvent, and(2) polymerizing the 1,3 butadiene monomer into syndiotactic1,2-polybutadiene within the rubber cement by using a chromium-based,molybdenum-based, or iron-based catalyst composition. The chromium-basedcatalyst composition is formed by combining (a) a chromium-containingcompound, (b) a hydrogen phosphite, and (c) an organomagnesium compound.The molybdenum-based catalyst composition is formed by combining (a) amolybdenum-containing compound, (b) a hydrogen phosphite, and (c) anorganoaluminum compound. The iron-based catalyst composition is formedby combining (a) an iron-containing compound, (b) a hydrogen phosphite,and (c) an organoaluminum compound.

[0019] The rubber cement employed in this invention is a solution,preferably viscous, of at least one rubbery elastomer in an organicsolvent. Virtually any type of rubbery elastomer can be used to preparethe rubber cement. In a preferred embodiment, the rubbery elastomerincludes an elastomeric terpolymer polymerized from ethylene, at leastone α-olefin monomer, and at least one diene monomer. The α-olefins mayinclude, but are not limited to, propylene, 1-butene, 1-hexene,4-methyl-1-pentene, 1-octene, 1-decene, or combinations thereof. Thediene monomers may include, but are not limited to,5-ethylidene-2-norbornene, 1,4-hexadiene, 5-methylene-2-norbornene,1,6-octadiene, 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene,1,3-cyclopentadiene, 1,4-cyclohexadiene, dicyclopentadiene,5-vinyl-2-norbornene and the like, or a combination thereof. When theterpolymer is polymerized from ethylene, propylene, and at least onediene monomer, the polymer may be referred to as EPDM.

[0020] Elastomeric terpolymers prepared from ethylene, at least oneα-olefin monomer, and at least one diene monomer may be prepared bymethods known in the art, and they are commercially available under thetradenames Vistalon™ (Exxon Mobil Chemical Co.; Houston, Tex.), Keltan™(DSM Copolymers; Baton Rouge, La.), Nordel™ IP (DuPont Dow Elastomers;Wilmington, Del.), ElastoFlo™ (Union Carbide; Danbury, Conn.), and Buna™(Bayer Corp.; Germany).

[0021] The elastomeric terpolymers described above may be used incombination with each other, or other rubbery elastomers. Examples ofother rubbery elastomers include, but are not limited to, naturalrubber, low-vinyl polybutadiene, cis-1,4-polybutadiene, amorphous1,2-polybutadiene, low-vinyl polyisoprene, cis-1,4-polyisoprene,polyisobutylene, neoprene, ethylene-propylene copolymer rubber (EPR),styrene-butadiene rubber (SBR), styrene-isoprene rubber (SIR),styrene-isoprene-butadiene rubber (SIBR), styrene-butadiene-styreneblock copolymer (SBS), styrene-butadiene block copolymer (SB),hydrogenated styrene butadiene-styrene block copolymer (SEBS),hydrogenated styrene-butadiene block copolymer (SE B),styrene-isoprene-styrene block copolymer (SIS), styrene-isoprene blockcopolymer (SI), hydrogenated styrene-isoprene-styrene block copolymer(SEPS), hydrogenated styrene-isoprene block copolymer (SEP), polysulfiderubber, acrylic rubber, urethane rubber, silicone rubber,epichlorohydrin rubber, and the like. Mixtures of the above rubberyelastomers may also be used. These rubbery elastomers are well knownand, for the most part, are commercially available. Also, those skilledin the art will be able to readily synthesize these rubbery elastomersby using techniques that are well known in the art.

[0022] The rubber cement can be prepared by dissolving the rubberyelastomers in an organic solvent. When commercially available rubberyelastomers are employed to prepare the rubber cement, it may benecessary to purify the commercial products before use in order toremove residual water and additives that may become catalyst poisons inthe subsequent step of polymerizing 1,3-butadiene monomer intosyndiotactic 1,2-polybutadiene within the rubber cement.

[0023] In one embodiment, the rubber cement is prepared in situ bypolymerizing one or more appropriate monomers into rubbery elastomers inan organic solvent within the same reactor that is subsequently used forpolymerizing 1,3-butadiene into syndiotactic 1,2-polybutadiene. Manymethods of synthesizing rubbery elastomers are known in the art.Preferably, however, the catalyst utilized in preparing the rubberyelastomers should not contain any ingredients that may interfere withthe catalyst subsequently used in the step of polymerizing 1,3-butadienemonomer into syndiotactic 1,2-polybutadiene within the rubber cement.

[0024] In preparing the rubber cement, it is desirable to select anorganic solvent that is inert with respect to the catalyst systems thatwill be employed to synthesize the rubbery elastomers and thesyndiotactic 1,2-polybutadiene. Suitable types of organic solvents thatcan be utilized in preparing the rubber cement include, but are notlimited to, aliphatic, cycloaliphatic, and aromatic hydrocarbons. Somerepresentative examples of suitable aliphatic solvents includen-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane,isopentane, isohexanes, isoheptanes, isooctanes, 2,2-dimethylbutane,petroleum ether, kerosene, petroleum spirits, and the like. Somerepresentative examples of suitable cycloaliphatic solvents includecyclopentane, cyelohexane, methylcyclopentane, methylcyclohexane, andthe like. Some representative examples of suitable aromatic solventsinclude benzene, toluene, xylenes, ethylbenzene, diethylbenzene,mesitylene, and the like. Commercial mixtures of the above hydrocarbonsmay also be used. For environmental reasons, aliphatic andcycloaliphatic solvents are highly preferred.

[0025] The concentration of the rubbery elastomers in the rubber cementvaries depending on the types of the rubbery elastomers and organicsolvent employed. The concentration of the rubbery elastomers within thecement is preferably from about 5% to about 35% by weight of the rubbercement, more preferably from about 10% to 30% by weight of the rubbercement, and even more preferably from about 15% to about 25% by weightof the rubber cement.

[0026] The rubber cement is then utilized as a polymerization medium forthe stereospecific polymerization of 1,3-butadiene monomer intosyndiotactic 1,2-polybutadiene. Thus, 1,3-butadiene monomer, catalystcomposition, and optionally additional organic solvent are added to therubber cement. The order in which the 1,3-butadiene monomer, thecatalyst composition, and the solvent are added to the rubber cementdoes not limit the scope of the invention, although it may be preferableto add the catalyst composition, or at least an ingredient thereof,prior to adding the 1,3-butadiene monomer.

[0027] The amount of 1,3-butadiene monomer added to the rubber cement iscontingent upon the proportion of syndiotactic 1,2-polybutadiene desiredin the resultant polymer blend. The additional organic solvent can beselected from the group of the organic solvents mentioned above for thepreparation of the rubber cement, and may be the same as or differentfrom the organic solvent used in preparing the rubber cement. Theaddition of 1,3-butadiene monomer to the rubber cement may not berequired in the case where 1,3-butadiene monomer is employed to preparethe rubbery elastomers and the polymerization is stopped before all the1,3-butadiene is consumed, thereby providing the remaining 1,3-butadienemonomer for synthesizing the syndiotactic 1,2-polybutadiene without theneed to add additional 1,3-butadiene monomer.

[0028] Although the preferred embodiment of the present invention isdirected toward the polymerization of 1,3-butadiene into syndiotactic1,2-polybutadiene within a rubber cement, other conjugated dienemonomers can be polymerized to form conjugated diene polymers,preferably crystalline polymers, within a rubber cement.

[0029] Chromium-based catalyst compositions useful for thepolymerization of 1,3-butadiene into syndiotactic 1,2-polybutadiene aredescribed in U.S. Pat. Nos. 6,201,080 and 6,117,956, which areincorporated herein by reference. The preferred chromium-based catalystcomposition is formed by combining (a) a chromium-containing compound,(b) a hydrogen phosphite, and (c) an organomagnesium compound. Inaddition to the three catalyst ingredients (a), (b), and (c), otherorganometallic compounds or Lewis bases that are known in the art canalso be added, if desired.

[0030] Various chromium-containing compounds or mixtures thereof can beemployed as ingredient (a) of the chromium-based catalyst compositionutilized in this invention. It is generally advantageous to employchromium-containing compounds that are soluble in a hydrocarbon solventsuch as aromatic hydrocarbons, aliphatic hydrocarbons, or cycloaliphatichydrocarbons. Hydrocarbon-insoluble chromium-containing compounds,however, can be suspended in the polymerization medium to form thecatalytically active species and are therefore also useful.

[0031] The chromium atom in the chromium-containing compounds can be invarious oxidation states ranging from 0 up to +6. Divalent chromiumcompounds (also called chromous compounds), wherein the chromium is inthe +2 oxidation state, and trivalent chromium compounds (also calledchromic compounds), wherein the chromium is in the +3 oxidation stateare preferred. Suitable types of chromiurr-containing compounds that canbe utilized include, but are not limited to, chromium carboxylates,chromium organophosphates, chromium organophosphonates, chromiumorganophosphinates, chromium carbamates, chromium dithiocarbamates,chromium xanthates, chromium β-diketonates, chromium alkoxides oraryloxides, chromium halides, chromium pseudo-halides, chromiumoxyhalides, and organochromium compounds.

[0032] Suitable chromium carboxylates include chromium formate, chromiumacetate, chromium acrylate, chromium methacrylate, chromium valerate,chromium gluconate, chromium citrate, chromium fumarate, chromiumlactate, chromium maleate, chromium oxalate, chromium 2-ethylhexanoate,chromium neodecanoate, chromium naphthenate, chromium stearate, chromiumoleate, chromium benzoate, and chromium picolinate.

[0033] Suitable chromium organophosphates include chromium dibutylphosphate, chromium dipentyl phosphate, chromium dihexyl phosphate,chromium diheptyl phosphate, chromium dioctyl phosphate, chromiumbis(1-methylheptyl) phosphate, chromium bis(2-ethylhexyl) phosphate,chromium didecyl phosphate, chromium didodecyl phosphate, chromiumdioctadecyl phosphate, chromium dioleyl phosphate, chromium diphenylphosphate, chromium bis(p-nonylphenyl) phosphate, chromiumbutyl(2-ethylhexyl) phosphate, chromium (1-methylheptyl)(2-ethylhexyl)phosphate, and chromium (2-ethylhexyl)(p-nonylphenyl) phosphate.

[0034] Suitable chromium organophosphonates include chromium butylphosphonate, chromium pentyl phosphonate, chromium hexyl phosphonate,chromium heptyl phosphonate, chromium octyl phosphonate, chromium (1methylheptyl) phosphonate, chromium (2-ethylhexyl) phosphonate, chromiumdecyl phosphonate, chromium dodecyl phosphonate, chromium octadecylphosphonate, chromium oleyl phosphonate, chromium phenyl phosphonate,chromium (p-nonylphenyl) phosphonate, chromium butyl butylphosphonate,10 chromium pentyl pentylphosphonate, chromium hexyl hexylphosphonate,chromium heptyl heptylphosphonate, chromium octyl octylphosphonate,chromium (1-methylheptyl) (1-methylheptyl)phosphonate, chromium(2-ethylhexyl) (2-ethylhexyl)phosphonate, chromium decyldecylphosphonate, chromium dodecyl dodecylphosphonate, chromiumoctadecyl octadecylphosphonate, chromium oleyl oleylphosphonate,chromium phenyl phenylphosphonate, chromium (p-nonylphenyl)(p-nonylphenyl)phosphonate, chromium butyl (2-ethylhexyl)phosphonate,chromium (2-ethylhexyl)butylphosphonate, chromium (1-methylheptyl)(2-ethylhexyl)phosphonate, chromium (2-ethylhexyl)(1-methylheptyl)phosphonate, chromium (2-ethylhexyl)(p-nonylphenyl)phosphonate, and chromium (p-nonylphenyl) (2-ethylhexyl)phosphonate.

[0035] Suitable chromium organophosphinates include chromiumbutylphosphinate, chromium pentylphosphinate, chromium hexylphosphinate,chromium heptylphosphinate, chromium octylphosphinate, chromium(1-methylheptyl) phosphinate, chromium (2-ethylhexyl)phosphinate,chromium decylphosphinate, chromium dodecylphosphinate, chromiumoctadecylphosphinate, chromium oleylphosphinate, chromiumphenylphosphinate, chromium (p-nonylphenyl)phosphinate, chromiumdibutylphosphinate, chromium dipentylphosphinate, chromiumdihexylphosphinate, chromium diheptylphosphinate, chromiumdioctylphosphinate, chromium bis(1-methylheptyl)phosphinate, chromiumbis(2-ethylhexyl)phosphinate, chromium didecylphosphinate, chromiumdidodecylphosphinate, chromium dioctadecylphosphinate, chromiumdioleylphosphinate, chromium diphenylphosphinate, chromiumbis(p-nonylphenyl)phosphinate, chromium butyl(2-ethylhexyl)phosphinate,chromium (1-methylheptyl)(2-ethylhexyl)phosphinate, and chromium(2-ethylhexyl)(p-nonylphenyl)phosphinate.

[0036] Suitable chromium carbamates include chromium dimethylcarbamate,chromium diethylcarbamate, chromium diisopropylcarbamate, chromiumdibutylcarbamate, and chromium dibenzylcarbamate.

[0037] Suitable chromium dithiocarbamates include chromiumdimethyldithiocarbamate, chromium diethyldithiocarbamate, chromiumdiisopropyldithiocarbamate, chromium dibutyldithiocarbamate, andchromium dibenzyldithiocarbamate.

[0038] Suitable chromium xanthates include chromium methylxanthate,chromium ethylxanthate, chromium isopropylxanthate, chromiumbutylxanthate, and chromium benzylxanthate.

[0039] Suitable chromium diketonates include chromium acetylacetonate,chromium trifluoroacetylacetonate, chromium hexafluoroacetylacetonate,chromium benzoylacetonate, chromium2,2,6,6-tetramethyl-3,5-heptanedionate, chromium dioxidebis(acetylacetonate), chromium dioxide bis(trifluoroacetylacetonate),chromium dioxide bis(hexafluoroacetylacetonate), chromium dioxidebis(benzoylacetonate), and chromium dioxidebis(2,2,6,6-tetramethyl-3,5-heptanedionate).

[0040] Suitable chromium alkoxides or aryloxides include chromiummethoxide, chromium ethoxide, chromium isopropoxide, chromium2-ethylhexoxide, chromium phenoxide, chromium nonylphenoxide, andchromium naphthoxide.

[0041] Suitable chromium halides include chromium hexafluoride, chromiumpentafluoride, chromium tetrafluoride, chromium trifluoride, chromiumpentachloride, chromium tetrachloride, chromium bichloride, chromiumtetrabromide, chromium tribromide, chromium triiodide, and chromiumdiiodide.

[0042] Suitable chromium pseudo-halides include chromium cyanide,chromium cyanate, chromium thiocyanate, and chromium azide.

[0043] Suitable chromium oxyhalides include chromium oxytetrafluoride,chromium dioxydifluoride, chromium oxytetrachloride, chromiumoxytrichloride, chromium dioxydichloride, chromium oxytribromide, andchromium dioxydibromide.

[0044] The term “organochromium compound” refers to any chromiumcompound containing at least one chromium-carbon bond. Suitableorganochromium compounds include tris(allyl)chromium,tris(methallyl)chromium, tris(crotyl) chromium,bis(cyclopentadienyl)chromium (also called chromocene),bis(pentamethylcyclopentadienyl)chromium, bis(ethylbenzene)chromium(also called decamethylchromocene), bis(benzene)chromium,bis(ethylbenzene)chromium, bis(mesitylene)chromium,bis(pentadienyl)chromium, bis(2,4-dimethylpentadienyl) chromium,bis(allyl)tricarbonylchromium, (cyclopentadienyl)(pentadienyl)chromium,terra(1-norbornyl)chromium, (trimethylenemethane)tetracarbonylchromium,bis(butadiene)dicarbonylchromium, (butadiene)tetracarbonylchromium, andbis(cyclooctatetraene)chromium.

[0045] Useful hydrogen phosphite compounds that can be employed asingredient (b) of the chromium-based catalyst composition utilized inthis invention are either acyclic hydrogen phosphites, cyclic hydrogenphosphites, or mixtures thereof.

[0046] In general, acyclic hydrogen phosphites may be represented by thefollowing keto-enol tautomeric structures:

[0047] where R₁ and R₂, which may be the same or different, aremono-valent organic groups. Preferably, R₁ and R₂ are hydrocarbyl groupssuch as, but not limited to, alkyl, cycloalkyl, substituted cycloalkyl,alkenyl, cycloalkenyl, substituted cycloalkenyl, aryl, allyl,substituted aryl, aralkyl, alkaryl, and alkynyl groups, with each grouppreferably containing from 1 carbon atom, or the appropriate minimumnumber of carbon atoms to form the group, up to 20 carbon atoms. Thesehydrocarbyl groups may contain heteroatoms such as, but not limited to,nitrogen, oxygen, silicon, sulfur, and phosphorus atoms. The acyclichydrogen phosphites exist mainly as the keto tautomer (shown on theleft), with the enol tautomer (shown on the right) being the minorspecies. The equilibrium constant for the above-mentioned tautomericequilibrium is dependent upon factors such as the temperature, the typesof R₁ and R₂ groups, the type of solvent, and the like. Both tautomersmay be associated in dimeric, trimeric or oligomeric forms by hydrogenbonding. Either of the two tautomers or mixtures thereof can be employedas the ingredient (b) of the chromium-based catalyst compositionutilized in this invention.

[0048] Suitable acyclic hydrogen phosphites include dimethyl hydrogenphosphite, diethyl hydrogen phosphite, dibutyl hydrogen phosphite,dihexyl hydrogen phosphite, dioctyl hydrogen phosphite, didecyl hydrogenphosphite, didodecyl hydrogen phosphite, dioctadecyl hydrogen phosphite,bis(2,2,2 trifluoroethyl) hydrogen phosphite, diisopropyl hydrogenphosphite, bis(3,3 dimethyl-2-butyl) hydrogen phosphite,bis(2,4-dimethyl-3-pentyl) hydrogen phosphite, di-t-butyl hydrogenphosphite, bis(2-ethylhexyl) hydrogen phosphite, dineopentyl hydrogenphosphite, bis(cyclopropylmethyl) hydrogen phosphite,bis(cyclobutylmethyl) hydrogen phosphite, bis(cyclopentylmethyl)hydrogen phosphite, bis(cyclohexylmethyl) hydrogen phosphite,dicyclobutyl hydrogen phosphite, dicyclopentyl hydrogen phosphite,dicyclohexyl hydrogen phosphite, dimethyl hydrogen phosphite, diphenylhydrogen phosphite, dinaphthyl hydrogen phosphite, dibenzyl hydrogenphosphite, bis(1-naphthylmethyl) hydrogen phosphite, diallyl hydrogenphosphite, dimethallyl hydrogen phosphite, dicrotyl hydrogen phosphite,ethyl butyl hydrogen phosphite, methyl hexyl hydrogen phosphite, methylneopentyl hydrogen phosphite, methyl phenyl hydrogen phosphite, methylcyclohexyl hydrogen phosphite, methyl benzyl hydrogen phosphite, and thelike. Mixtures of the above dihydrocarbyl hydrogen phosphites may alsobe utilized.

[0049] In general, cyclic hydrogen phosphites contain a divalent organicgroup that bridges between the two oxygen atoms that are singly-bondedto the phosphorus atoms. These cyclic hydrogen phosphites may berepresented by the following keto-enol tautomeric structures:

[0050] where R₃ is a divalent organic group. Preferably, R₃ is ahydrocarbylene group such as, but not limited to, alkylene,cydoalkylene, substituted alkylene, substituted cycloalkylene,alkenylene, cycoalkenylene, substituted alkenylene, substitutedcycloalkenylene, arylene, and substituted arylene groups, with eachgroup preferably containing from 1 carbon atom, or the appropriateminimum number of carbon atoms to form the group, up to 20 carbon atoms.These hydrocarbylene groups may contain heteroatoms such as, but notlimited to, nitrogen, oxygen, silicon, sulfur, and phosphorus atoms. Thecyclic hydrogen phosphites exist mainly as the keto tautomer (shown onthe left), with the enol tautomer (shown on the right) being the minorspecies. The equilibrium constant for the above-mentioned tautomericequilibrium is dependent upon factors such as the temperature, the typesof R₃ group, the type of solvent, and the like. Both tautomers may beassociated in dimeric, trimeric or oligomeric forms by hydrogen bonding.Either of the two tautomers or mixtures thereof can be employed as theingredient (b) of the chromium-based catalyst composition utilized inthis invention.

[0051] The cyclic hydrogen phosphites may be synthesized by thetransesterification reaction of an acyclic dihydrocarbyl hydrogenphosphite (usually dimethyl hydrogen phosphite or diethyl hydrogenphosphite) with an alkylene diol or an arylene diol. Procedures for thistransesterification reaction are well known to those skilled in the art.Typically, the transesterification reaction is carried out by heating amixture of an acyclic dihydrocarbyl hydrogen phosphite and an alkylenediol or an arylene diol. Subsequent distillation of the side-productalcohol (usually methanol or ethanol) that results from thetransesterification reaction leaves the new-made cyclic hydrogenphosphite.

[0052] Suitable cyclic alkylene hydrogen phosphites include2-oxo-(2H)-5-butyl-5-ethyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-5,5-dimethyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-1,3,2-dioxaphosphorinane, 2-oxo-(2H)-4-methyl1,3,2-dioxaphosphorinane,2-oxo-(2H)-5-ethyl-5-methyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-5,5-diethyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-5-methyl-5-propyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-4-isopropyl-5,5-dimethyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-4,6-dimethyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-4-propyl-5-ethyl-1,3,2-dioxaphosphorinane,2-oxo-(2H)-4-methyl-1,3,2-dioxaphospholane,2-oxo-(2H)-4,5-dimethyl-1,3,2-dioxaphospholane,2-oxo-(2H)-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane, and the like.Mixtures of the above cyclic alkylene hydrogen phosphites may also beutilized.

[0053] Suitable cyclic arylene hydrogen phosphites include2-oxo-(2H)-4,5-benzo-1,3,2-dioxaphospholane,2-oxo-(2H)-4,5-(3′-methylbenzo)-1,3,2-dioxaphospholane,2-oxo-(2H)-4,5-(4′-methylbenzo)-1,3,2-dioxaphospholane,2-oxo-(2H)-4,5-(4′-tert-butylbenzo)-1,3,2-dioxaphospholane,2-oxo-(2H)-4,5-naphthalo-1,3,2-dioxaphospholane, and the like. Mixturesof the above cyclic arylene hydrogen phosphites may also be utilized.

[0054] The chromium-based catalyst composition utilized in thisinvention further comprises an organomagnesium compound, which has beendesignated as ingredient (c). As used herein, the term “organomagnesiumcompound” refers to any magnesium compound containing at least onemagnesium-carbon bond. Organomagnesium compounds that are soluble in ahydrocarbon solvent are preferably employed.

[0055] A preferred class of organomagnesium compounds that can beutilized as ingredient (c) of the chromium-based catalyst compositionutilized in this invention is represented by the general formulaMg(R₄)₂, where each R₄, which may be the same or different, is amono-valent organic group, with the proviso that the group is attachedto the magnesium atom via a carbon atom. Preferably, each R₄ is ahydrocarbyl group such as, but not limited to, alkyl, cycloalkyl,substituted cycloalkyl, alkenyl, cydoalkenyl, substituted cydoalkenyl,aryl, allyl, substituted aryl, aralkyl, alkaryl, and alkynyl groups,with each group preferably containing from 1 carbon atom, or theappropriate minimum number of carbon atoms to form the group, up toabout 20 carbon atoms. These hydrocarbyl groups may contain heteroatomssuch as, but not limited to, nitrogen, oxygen, silicon, sulfur, andphosphorus atom.

[0056] Suitable dihydrocarbylmagnesium compounds includediethylmagnesium, di-n-propylmagnesium, diisopropylmagnesium,dibutylmagnesium, dihexylmagnesium, diphenylmagnesium,dibenzylmagnesium, and mixtures thereof. Dibutylmagnesium isparticularly useful due to its availability and its solubility inaliphatic and cycloaliphatic hydrocarbon solvents.

[0057] Another class of organomagnesium compounds that can be utilizedas ingredient (c) of the catalyst composition utilized in this inventionis represented by the general formula R₅MgX, where R₅ is a mono-valentorganic group, with the proviso that the group is attached to themagnesium atom via a carbon atom, and X is a hydrogen atom, a halogenatom, a carboxylate group, an alkoxide group, or an aryloxide group.Preferably, R₅ is a hydrocarbyl group such as, but not limited to,alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, cycloalkenyl,substituted cycloalkenyl, aryl, allyl, substituted aryl, aralkyl,alkaryl, and alkynyl groups, with each group preferably containing from1 carbon atom, or the appropriate minimum number of carbon atoms to formthe group, up to about 20 carbon atoms. These hydrocarbyl groups maycontain heteroatoms such as, but not limited to, nitrogen, oxygen,silicon, sulfur, and phosphorus atoms. Preferably, X is a carboxylategroup, an alkoxide group, or an aryloxide group, with each grouppreferably containing 1 to 20 carbon atoms.

[0058] Suitable types of organomagnesium compounds that are representedby the general formula R₅MgX include, but are not limited to,hydrocarbylmagnesium hydride, hydrocarbylmagnesium halide,hydrocarbylmagnesium carboxylate, hydrocarbylmagnesium alkoxide,hydrocarbylmagnesium aryloxide, and mixtures thereof.

[0059] Suitable organomagnesium compounds that are represented by thegeneral formula R₅MgX include methylmagnesium hydride, ethylmagnesiumhydride, butylmagnesium hydride, hexylmagnesium hydride, phenylmagnesiumhydride, benzylmagnesium hydride, methylmagnesium chloride,ethylmagnesium chloride, butylmagnesium chloride, hexylmagnesiumchloride, phenylmagnesium chloride, benzylmagnesium chloride,methylmagnesium bromide, ethylmagnesium bromide, butylmagnesium bromide,hexylmagnesium bromide, phenylmagnesium bromide, benzylmagnesiumbromide, methylmagnesium hexanoate, ethylmagnesium hexanoate,butylmagnesium hexanoate, hexylmagnesium hexanoate, phenylmagnesiumhexanoate, benzylmagnesium hexanoate, methylmagnesium ethoxide,ethylmagnesium ethoxide, butylmagnesium ethoxide, hexylmagnesiumethoxide, phenylmagnesium ethoxide, benzylmagnesium ethoxide,methylmagnesium phenoxide, ethylmagnesium phenoxide, butylmagnesiumphenoxide, hexylmagnesium phenoxide, phenylmagnesium phenoxide,benzylmagnesium phenoxide, and the like, and mixtures thereof.

[0060] Molybdenum-based catalyst compositions are described in U.S. Ser.No. 09/700,017, which is incorporated herein by reference. Themolybdenum-based catalyst composition is formed by combining (a) amolybdenum-containing compound, (b) a hydrogen phosphite, and (c) anorganoaluminum compound. In addition to the three catalyst ingredients(a), (b), and (c), other organometallic compounds or Lewis bases canalso be added, if desired.

[0061] Various molybdenum-containing compounds or mixtures thereof canbe employed as ingredient (a) of the catalyst composition utilized inthis invention. It is generally advantageous to employmolybdenum-containing compounds that are soluble in hydrocarbon solventssuch as aromatic hydrocarbons, aliphatic hydrocarbons, or cycloaliphatichydrocarbons. Hydrocarbon insoluble molybdenum-containing compounds,however, can be suspended in the polymerization medium to form thecatalytically active species and are therefore also useful.

[0062] The molybdenum atom in the molybdenum-containing compounds can bein various oxidation states ranging from 0 up to +6. Suitable types ofmolybdenum-containing compounds that can be utilized include, but arenot limited to, molybdenum carboxylates, molybdenum organophosphates,molybdenum organophosphonates, molybdenum organophosphinates, molybdenumcarbamates, molybdenum dithiocarbamates, molybdenum xanthates,molybdenum β-diketonates, molybdenum alkoxides or aryloxides, molybdenumhalides, molybdenum pseudo-halides, molybdenum oxyhalides, andorganomolybdenum compounds.

[0063] Suitable molybdenum carboxylates include molybdenum formate,molybdenum acetate, molybdenum acrylate, molybdenum methacrylate,molybdenum valerate, molybdenum gluconate, molybdenum citrate,molybdenum fumarate, molybdenum lactate, molybdenum maleate, molybdenumoxalate, molybdenum 2-ethylhexanoate, molybdenum neodecanoate,molybdenum naphthenate, molybdenum stearate, molybdenum oleate,molybdenum benzoate, and molybdenum picolinate.

[0064] Suitable molybdenum organophosphates include molybdenum dibutylphosphate, molybdenum dipentyl phosphate, molybdenum dihexyl phosphate,molybdenum dibeptyl phosphate, molybdenum dioctyl phosphate, molybdenumbis(1-methylheptyl) phosphate, molybdenum bis(2-ethylhexyl) phosphate,molybdenum didecyl phosphate, molybdenum didodecyl phosphate, molybdenumdioctadecyl phosphate, molybdenum dioleyl phosphate, molybdenum diphenylphosphate, molybdenum bis(p-nonylphenyl) phosphate, molybdenum butyl (2ethylhexyl) phosphate, molybdenum (1-methylheptyl) (2-ethylhexyl)phosphate, and molybdenum (2-ethylhexyl) (p-nonylphenyl) phosphate.

[0065] Suitable molybdenum organophosphonates include molybdenum butylphosphonate, molybdenum pentyl phosphonate, molybdenum hexylphosphonate, molybdenum heptyl phosphonate, molybdenum octylphosphonate, molybdenum (1-methylheptyl) phosphonate, molybdenum(2-ethylhexyl) phosphonate, molybdenum decyl phosphonate, molybdenumdodecyl phosphonate, molybdenum octadecyl phosphonate, molybdenum oleylphosphonate, molybdenum phenyl phosphonate, molybdenum (p-nonylphenyl)phosphonate, molybdenum butyl butylphosphonate, molybdenum pentylpentylphosphonate, molybdenum hexyl hexylphosphonate, molybdenum heptylheptylphosphonate, molybdenum octyl octylphosphonate, molybdenum(1-methylheptyl) (1-methylheptyl)phosphonate, molybdenum (2-ethylhexyl)(2-ethylhexyl) phosphonate, molybdenum decyl decylphosphonate,molybdenum dodecyl dodecylphosphonate, molybdenum octadecyloctadecylphosphonate, molybdenum oleyl oleylphosphonate, molybdenumphenyl phenylphosphonate, molybdenum (p-nonylphenyl)(p-nonylphenyl)phosphonate, molybdenum butyl (2-ethylhexyl)phosphonate,molybdenum (2-ethylhexyl) butylphosphonate, molybdenum (1-methylheptyl)(2-ethylhexyl)phosphonate, molybdenum (2-ethylhexyl)(1-methylheptyl)phosphonate, molybdenum (2-ethylhexyl)(p-nonylphenyl)phosphonate, and molybdenum (p-nonylphenyl)(2-ethylhexyl) phosphonate.

[0066] Suitable molybdenum organophosphinates include molybdenumbutylphosphinate, molybdenum pentylphosphinate, molybdenumhexylphosphinate, molybdenum heptylphosphinate, molybdenumoctylphosphinate, molybdenum (1-methylheptyl)phosphinate, molybdenum(2-ethylhexyl)phosphinate, molybdenum decylphosphinate, molybdenumdodecylphosphinate, molybdenum octadecylphosphinate, molybdenumoleylphosphinate, molybdenum phenylphosphinate, molybdenum(p-nonylphenyl)phosphinate, molybdenum dibutylphosphinate, molybdenumdipentylphosphinate, molybdenum dihexylphosphinate, molybdenumdiheptylphosphinate, molybdenum dioctylphosphinate, molybdenumbis(1-methylheptyl)phosphinate, molybdenum bis(2-ethylhexyl)phosphinate,molybdenum didecylphosphinate, molybdenum didodecylphosphinate,molybdenum dioctadecylphosphinate, molybdenum dioleylphosphinate,molybdenum diphenylphosphinate, molybdenumbis(p-nonylphenyl)phosphinate, molybdenumbutyl(2-ethylhexyl)phosphinate, molybdenum (1-methylheptyl)(2-ethylhexyl)phosphinate, and molybdenum (2-ethylhexyl) (p-nonylphenyl)phosphinate.

[0067] Suitable molybdenum carbamates include molybdenumdimethylcarbamate, molybdenum diethylcarbamate, molybdenumdiisopropylcarbamate, molybdenum dibutylcarbamate, and molybdenumdibenzylcarbamate.

[0068] Suitable molybdenum dithiocarbamates include molybdenumdimethyldithiocarbamate, molybdenum diethyldithiocarbamate, molybdenumdiisopropyldithiocarbamate, molybdenum dibutyidithiocarbamate, andmolybdenum dibenzyldithiocarbamate.

[0069] Suitable molybdenum xanthates include molybdenum methylxanthate,molybdenum ethylxanthate, molybdenum isopropylxanthate, molybdenumbutylxanthate, and molybdenum benzylxanthate.

[0070] Suitable molybdenum p-diketonates include molybdenumacetylacetonate, molybdenum trifluoroacetylacetonate, molybdenumhexafluoroacetylacetonate, molybdenum benzoylacetonate, molybdenum2,2,6,6-tetramethyl-3,5-heptanedionate, molybdenum dioxidebis(acetylacetonate), molybdenum dioxide bis(trifluoroacetylacetonate),molybdenum dioxide bis(hexafluoroacetylacetonate), molybdenum dioxidebis(benzoylacetonate), and molybdenum dioxidebis(2,2,6,6-tetramethyl-3,5-heptanedionate).

[0071] Suitable molybdenum alkoxides or aryloxides include molybdenummethoxide, molybdenum ethoxide, molybdenum isopropoxide, molybdenum2-ethylhexoxide, molybdenum phenoxide, molybdenum nonylphenoxide, andmolybdenum naphthoxide.

[0072] Suitable molybdenum halides include molybdenum hexafluoride,molybdenum pentafluoride, molybdenum tetrafluoride, molybdenumtrifluoride, molybdenum pentachloride, molybdenum tetrachloride,molybdenum bichloride, molybdenum tetrabromide, molybdenum tribromide,molybdenum triiodide, and molybdenum diiodide.

[0073] Suitable molybdenum pseudo-halides include molybdenum cyanide,molybdenum cyanate, molybdenum thiocyanate, and molybdenum azide.

[0074] Suitable molybdenum oxyhalides include molybdenumoxytetrafluoride, molybdenum dioxydifluoride, molybdenumoxytetrachloride, molybdenum oxytrichloride, molybdenum dioxydichloride,molybdenum oxytribromide, and molybdenum dioxydibromide.

[0075] The term “organomolybdenum compound” refers to any molybdenumcompound containing at least one molybdenum-carbon bond. Some specificexamples of suitable organomolybdenum compounds includetris(allyl)molybdenum, tris(methallyl)molybdenum,tris(crotyl)molybdenum, bis(cyclopentadienyl)molybdenum,bis(pentamethylcydopentadienyl) molybdenum, bis(ethylbenzene)molybdenum,bis(mesitylene)molybdenum, bis(pentadienyl)molybdenum,bis(2,4-dimethylpentadienyl)molybdenum, bis(allyl)tricarbonylmolybdenum,(cyclopentadienyl) (pentadienyl) molybdenum,tetra(1-norbornyl)molybdenum (trimethylenemethane)tetracarbonylmolybdenum, bis(butadiene)dicarbonylmolybdenum, (butadiene)tetracarbonylmolybdenum, and bis(cyclooctatetraene)molybdenum.

[0076] Useful hydrogen phosphite compounds that can be employed asingredient (b) of the molybdenum-based catalyst composition utilized inthis invention are either acyclic hydrogen phosphites, cyclic hydrogenphosphites, or mixtures thereof. These compounds are described above.

[0077] The molybdenum-based catalyst composition further comprises anorganoaluminum compound, which has been designated as ingredient (c). Asused herein, the term “organoaluminum compound” refers to any aluminumcompound containing at least one aluminum-carbon bond. Organoaluminumcompounds that are soluble in a hydrocarbon solvent are preferablyemployed.

[0078] A preferred class of organoaluminum compounds is represented bythe general formula AlR_(n)X_(3-n) where each R, which may be the sameor different, is a mono-valent organic group that is attached to thealuminum atom via a carbon atom, where each X, which may be the same ordifferent, is a hydrogen atom, a halogen atom, a carboxylate group, analkoxide group, or an aryloxide group, and where n is an integer of 1 to3. Preferably, each R is a hydrocarbyl group such as, but not limitedto, alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, cycloalkenyl,substituted cycloalkenyl, aryl, allyl, substituted aryl, aralkyl,alkaryl, and alkynyl groups, with each group preferably containing from1 carbon atom, or the appropriate minimum number of carbon atoms to formthe group, up to about 20 carbon atoms. These hydrocarbyl groups maycontain heteroatoms such as, but not limited to, nitrogen, oxygen,silicon, sulfur, and phosphorus atoms. Preferably, each X is acarboxylate group, an alkoxide group, or an aryloxide group, with eachgroup preferably containing from 1 carbon atom, or the appropriateminimum number of carbon atoms to form the group, up to about 20 carbonatoms.

[0079] Suitable types of organoaluminum compounds that can be utilizedinclude, but are not limited to, trihydrocarbylaluminum,dibydrocarbylaluminum hydride, hydrocarbylaluminum dihydride,hydrocarbylaluminum dihalide, dihydrocarbylaluminum halide,dihydrocarbylaluminum carboxylate, hydrocarbylaluminum bis(carboxylate),dihydrocarbylaluminum alkoxide, hydrocarbylaluminum dialkoxide,dihydrocarbylaluminum aryloxide, hydrocarbylaluminum diaryloxide, andthe like, and mixtures thereof. Trihydrocarbylaluminum compounds aregenerally preferred.

[0080] Suitable organoaluminum compounds include trimethylaluminum,triethylaluminum, triisobutylaluminum, tri-n-propylaluminum,triisopropylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum,tri-n-octylaluminum, tricyclohexylaluminum, triphenylaluminum,tri-p-tolylaluminum, tribenzylaluminum, diethylphenylaluminum,diethyl-p-tolylaluminum, diethylbenzylaluminum, ethyldiphenylaluminum,ethyldi-p-tolylaluminum, ethyldibenzylaluminum, diethylaluminum hydride,di-n-propylaluminum hydride, diisopropylaluminum hydride,di-n-butylaluminum hydride, diisobutylaluminum hydride,di-n-octylaluminum hydride, diphenylaluminum hydride, di-p-tolylaluminum hydride, dibenzylaluminum hydride, phenylethylaluminum hydride,phenyl-n-propylaluminum hydride, phenylisopropylaluminum hydride,phenyl-n-butylaluminum hydride, phenylisobutylaluminum hydride, phenyl-noctylaluminum hydride, p-tolylethylaluminum hydride,p-tolyl-n-propylaluminum hydride, p-tolylisopropylaluminum hydride,p-tolyl-n-butylaluminum hydride, p-5-tolyl-isobutylaluminum hydride,p-tolyl-n-octylaluminum hydride, benzylethylaluminum hydride,benzyl-n-propylaluminum hydride, benzylisopropylaluminum hydride,benzyl-n-butylaluminum hydride, benzylisobutylaluminum hydride, andbenzyl-n-octylaluminum hydride, ethylaluminum dihydride,n-propylaluminum dibydride, isopropylaluminum dihydride, n-butylaluminumdihydride, isobutylaluminum dihydride, n-octylaluminum dibydri de,dimethylaluminum chloride, diethyl aluminum chloride, diisobutylaluminumchloride, dimethylaluminum bromide, diethylaluminum bromide,dimethylaluminum fluoride, diethylaluminum fluoride, methylaluminumdichloride, ethylaluminum dichloride, isobutyl aluminum dichloride,methylaluminum dibromide, ethylaluminum dibromide, methylaluminumdifluoride, ethylaluminum difluoride, methylaluminum sesquichloride,ethylaluminum sesquichloride, isobutylaluminum sesquichloride,dimethylaluminum hexanoate, diethylaluminum octoate, diisobutylaluminum2-ethylhexanoate, dimethylaluminum neodecanoate, diethylaluminumstearate, diisobutylaluminum oleate, methylaluminum bis(hexanoate),ethylaluminum bis(octoate), isobutylaluminum bis(2-ethylhexanoate),methyl-aluminum bis(neodecanoate), ethylaluminum bis(stearate),isobutylaluminum bis(oleate), dimethylaluminum methoxide,diethylaluminum methoxide, diisobutylaluminum methoxide,dimethylaluminum ethoxide, diethylaluminum ethoxide, diisobutylaluminumethoxide, dimethylaluminum phenoxide, diethylaluminum phenoxide,diisobutylaluminum phenoxide, methylaluminum dimethoxide, ethylaluminumdimethoxide, isobutylaluminum dimethoxide, methylaluminum diethoxide,ethylaluminum diethoxide, isobutylaluminum diethoxide, methylaluminumdiphenoxide, ethylaluminum diphenoxide, isobutylaluminum diphenoxide,and the like, and mixtures thereof.

[0081] Another class of organoaluminum compounds that can be utilized isaluminoxanes. Aluminoxanes are well known in the art and compriseoligomeric linear aluminoxanes that can be represented by the generalformula:

[0082] and oligomeric cyclic aluminoxanes that can be represented by thegeneral formula:

[0083] where x is an integer of 1 to about 100, preferably about 10 toabout 50; y is an integer of 2 to about 100, preferably about 3 to about20; and each R₆, which may be the same or different, is a mono-valentorganic group that is attached to the aluminum atom via a carbon atom.Preferably, each R₆ is a hydrocarbyl group such as, but not limited to,alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, cycloalkenyl,substituted cycloalkenyl, aryl, allyl, substituted aryl, aralkyl,alkaryl, and alkynyl groups, with each group preferably containing from1 carbon atoms, or the appropriate minimum number of carbon atoms toform the group, up to about 20 carbon atoms. These hydrocarbyl groupsmay contain heteroatoms such as, but not limited to, nitrogen, oxygen,silicon, sulfur, and phosphorus atoms. It should be noted that thenumber of moles of the aluminoxane as used in this application refers tothe number of moles of the aluminum atoms rather than the number ofmoles of the oligomeric aluminoxane molecules. This convention iscommonly employed in the art of catalysis utilizing aluminoxanes.

[0084] In general, aluminoxanes can be prepared by reactingtrihydrocarbylaluminum compounds with water. This reaction can beperformed according to known methods, such as (1) a method in which thetrihydrocarbylaluminum compound is dissolved in an organic solvent andthen contacted with water, (2) a method in which thetrihydrocarbylaluminum compound is reacted with water of crystallizationcontained in, for example, metal salts, or water adsorbed in inorganicor organic compounds, and (3) a method in which thetrihydrocarbylaluminum compound is added to the monomer or monomersolution that is to be oligomerized, and then water is added.

[0085] Examples of aluminoxane compounds include methylaluminoxane(MAO), modified methylaluminoxane (MMAO), ethylaluminoxane,butylaluminoxane, isobutylaluminoxane, and the like, and mixturesthereof. Isobutylaluminoxane is particularly useful on the grounds ofits availability and its solubility in aliphatic and cycloaliphatichydrocarbon solvents. Modified methylaluminoxane can be formed bysubstituting about 20-80% of the methyl groups of methylaluminoxane withC₂ to C₁₂ hydrocarbyl groups, preferably with isobutyl groups, by usingtechniques known to those skilled in the art.

[0086] Iron-based catalyst compositions are described in co-pendingpatent application U.S. Ser. No. 09/172,305, and U.S. Pat. Nos.6,180,734 and 6,211,313, which are incorporated herein by reference. Theiron-based catalyst compositions are formed by combining (a) aniron-containing compound, (b) a hydrogen phosphite, and (c) anorganoaluminum compound.

[0087] Various iron-containing compounds or mixtures thereof can beemployed as ingredient (a) of the iron-based catalyst compositionutilized in this invention. Iron-containing compounds that are solublein a hydrocarbon solvent such as aromatic hydrocarbons, aliphatichydrocarbons, or cycloaliphatic hydrocarbons are preferably used.Hydrocarbon-insoluble iron-containing compounds, however, can besuspended in the polymerization medium to form the catalytically activespedes, and are therefore also useful.

[0088] The iron atom in the iron-containing compounds can be in variousoxidation states including, but not limited to, the 0, +2, +3, and +4oxidation states. Divalent iron compounds (also called ferrouscompounds), wherein the iron is in the +2 oxidation state, and trivalentiron compounds (also called ferric compounds), wherein the iron is inthe +3 oxidation state are preferred. Suitable types of iron-containingcompounds that can be utilized in this invention include, but are notlimited to, iron carboxylates, iron carbamates, iron dithiocarbamates,iron xanthates, iron β-diketonates, iron alkoxides, iron aryloxides, andorganoiron compounds.

[0089] Suitable iron carboxylates include iron (II) formate, iron(III)formate, iron(II) acetate, iron(III) acetate, iron(II) acrylate,iron(III) acrylate, iron(II) methacrylate, iron(III) methacrylate,iron(II) valerate, iron(III) valerate, iron(II) gluconate, iron(III)gluconate, iron(II) citrate, iron(III) citrate, iron(II) fumarate,iron(III) fumarate, iron(II) lactate, iron(III) lactate, iron(II)maleate, iron(III) maleate, iron(II) oxalate, iron(III) oxalate,iron(II) 2-ethylhexanoate, iron(III) 2-ethylhexanoate, iron(II)neodecanoate, iron(III) neodecanoate, iron(II) naphthenate, iron(III)naphthenate, iron(II) stearate, iron(III) stearate, iron(II) oleate,iron(III) oleate, iron(II) benzoate, iron(III) benzoate, iron(II)picolinate, and iron (III) picolinate.

[0090] Suitable iron carbamates include iron (II) dimethylcarbamate,iron(III) dimethylcarbamate, iron(II) diethylcarbamate, iron(III)diethylcarbamate, iron(II) diisopropylcarbamate, iron(III)diisopropylcarbamate, iron(II) dibutylcarbamate, iron(III)dibutylcarbamate, iron(II) dibenzylcarbamate, and iron(III)dibenzylcarbamate.

[0091] Suitable iron dithiocarbamates include iron(II)dimethyldithiocarbamate, iron(III) dimethyldithiocarbamate, iron(II)diethyldithiocarbamate, iron(III) diethyldithiocarbamate, iron(II)diisopropyldithiocarbamate, iron(III) diisopropyldithiocarbamate,iron(II) dibutyidithiocarbamate, iron(III) dibutyidithiocarbamate,iron(II) dibenzyldithiocarbamate, and iron (III)dibenzyldithiocarbamate.

[0092] Suitable iron xanthates include iron (II) methylxanthate,iron(III) methylxanthate, iron(II) ethylxanthate, iron(III)ethylxanthate, iron(II) isopropylxanthate, iron(III) isopropylxanthate,iron(II) butylxanthate, iron(III) butylxanthate, iron(II)benzylxanthate, and iron(III) benzylxanthate.

[0093] Suitable iron β-diketonates include iron (II) acetylacetonate,iron (III) acetylacetonate, iron(II) trifluoroacetylacetonate, iron(III)trifluoroacetylacetonate, iron(II) hexafluoroacetylacetonate, iron(III)hexafluoroacetylacetonate, iron(II) benzoylacetonate, iron(III)benzoylacetonate, iron(II) 2,2,6,6-tetramethyl-3,5-heptanedionate, andiron(III) 2,2,6,6-tetramethyl-3,5-heptanedionate.

[0094] Suitable iron alkoxides or aryloxides include iron(II) methoxide,iron(III) methoxide, iron(II) ethoxide, iron(III) ethoxide, iron(II)isopropoxide, iron(III) isopropoxide, iron(II) 2-ethylhexoxide,iron(III) 2-ethylhexoxide, iron(II) phenoxide, iron(III) phenoxide,iron(II) nonylphenoxide, iron(III) nonylphenoxide, iron(II) naphthoxide,and iron(III) naphthoxide.

[0095] The term “organoiron compound” refers to any iron compoundcontaining at least one iron-carbon bond. Some specific examples ofsuitable organoiron compounds include bis(cyclopentadienyl)iron(II)(also called ferrocene), bis(pentamethylcyclopentadienyl)iron(II) (alsocalled decamethylferrocene), bis(pentadienyl) iron (II),bis(2,4-dimethylpentadienyl) iron (II), bis(allyl) dicarbonyliron (II),(cyclopentadienyl) (pentadienyl)iron(II), tetra(1-norbornyl)iron(IV),(trimethylenemethane)tricarbonyliron(II), bis(butadiene)carbonyliron(O),butadienetricarbonyliron(O), and bis(cyclooctatetraene)iron(O).

[0096] Useful hydrogen phosphite compounds that can be employed asingredient (b) of the iron-based catalyst composition utilized in thisinvention are either acyclic hydrogen phosphite, cyclic hydrogenphosphites, or mixtures thereof. These compounds are described above.

[0097] Useful organoaluminum compounds that can be employed asingredient (c) of the molybdenum-based catalyst composition, describedabove, are also suitable for use as ingredient (c) of the iron-basedcatalyst composition.

[0098] The catalyst compositions utilized in this invention have veryhigh catalytic activity for polymerizing 1,3-butadiene into syndiotactic1,2-polybutadiene over a wide range of total catalyst concentrations andcatalyst ingredient ratios. The polymers having the most desirableproperties, however, are obtained within a narrower range of totalcatalyst concentrations and catalyst ingredient ratios. Further, it isbelieved that the three catalyst ingredients (a), (b), and (c) caninteract to form an active catalyst species. Accordingly, the optimumconcentration for any one catalyst ingredient is dependent upon theconcentrations of the other catalyst ingredients.

[0099] With respect to the chromium-based catalyst composition, themolar ratio of the hydrogen phosphite to the chromium-containingcompound (P/Cr) can be varied from about 0.5:1 to about 50:1, morepreferably from about 1:1 to about 25:1, and even more preferably fromabout 2:1 to about 10:1. The molar ratio of the organomagnesium compoundto the chromium-containing compound (Mg/Cr) can be varied from about 1:1to about 50:1, more preferably from about 2:1 to about 30:1, and evenmore preferably from about 3:1 to about 20:1.

[0100] With respect to the molybdenum-based or iron-based catalystcompositions, the molar ratio of the hydrogen phosphite to themolybdenum containing compound (P/Mo) or to the iron-containing compound(P/Fe) can be varied from about 0.5:1 to about 50:1, more preferablyfrom about 1:1 to about 25:1, and even more preferably from about 2:1 toabout 10:1. Where ingredient (c) of the catalyst composition comprisesan organoaluminum compound defined by the formula AlR_(n)X_(3-n), themolar ratio of the organoaluminum compound to the molybdenum-containingcompound (Al/Mo) or to the iron-containing compound (Al/Fe) can bevaried from about 1:1 to about 100:1, more preferably from about 3:1 toabout 50:1, and even more preferably from about 5:1 to about 25:1. Wheningredient (c) of the catalyst composition utilized in the presentinvention comprises an aluminoxane, the molar ratio of the aluminoxaneto the molybdenum-containing compound (Al/Mo) or to the iron-containingcompound (Al/Fe) can be varied from about 5:1 to about 500:1, morepreferably from about 10:1 to about 200:1, and even more preferably fromabout 20:1 to about 100:1.

[0101] The catalyst composition is preferably formed by combining thethree catalyst ingredients (a), (b), and (c). Although an activecatalyst species is believed to result from this combination, the degreeof interaction or reaction between the various ingredients or componentsis not known with any great degree of certainty. Therefore, it should beunderstood that the term “catalyst composition” has been employed toencompass a simple mixture of the ingredients, a complex of the variousingredients that is caused by physical or chemical forces of attraction,a chemical reaction product of the ingredients, or a combination of theforegoing.

[0102] The catalyst composition utilized to prepare the syndiotactic1,2-polybutadiene can be formed by combining or mixing the catalystingredients or components by using, for example, one of the followingmethods:

[0103] First, the catalyst composition may be formed in situ by addingthe three catalyst ingredients to the rubber cement containing therubbery elastomerand 1,3-butadiene monomer in either a stepwise orsimultaneous manner. When adding the catalyst ingredients in a stepwisemanner, the sequence in which the ingredients are added is not critical.With regard to the chromium-based catalyst, the organomagnesium compoundis preferably added first, followed by the chromium-containing compound,and then followed by the hydrogen phosphite. With regard to themolybdenum-based or iron-based catalyst, the molybdenum-containing oriron-containing compound is preferably added first, followed by thehydrogen phosphite, and then followed by the organoaluminum compound.

[0104] Second, the three catalyst ingredients may be pre-mixed outsidethe polymerization system at an appropriate temperature, which isgenerally from about −20° C. to about 80° C., and the resulting catalystcomposition is then added to the rubber cement containing the rubberyelastomer and 1,3-butadiene monomer.

[0105] Third, the catalyst composition may be pre-formed in the presenceof conjugated diene monomer. That is, the three catalyst ingredients arepre-mixed in the presence of a small amount of conjugated diene monomerat an appropriate temperature, which is generally from about −20° C. toabout 80° C. The amount of 1,3-butadiene monomer that is used for thecatalyst pre-forming can range from about 1 to about 500 moles, morepreferably from about 4 to about 100 moles, and even more preferablyfrom about 10 to about 50 moles per mole of the chromium-containing,molybdenum-containing, or iron-containing compound. The resultingcatalyst composition is then added to the rubber cement containing therubbery elastomer and the 1,3-butadiene monomer that is to bepolymerized.

[0106] Fourth, as a further variation, the catalyst composition can alsobe formed by using a two-stage procedure. The first stage involvescombining the chromium-containing compound and the organomagnesiumcompound or the molybdenum-containing or iron-containing compound andthe organoaluminum compound, in the presence of a small amount ofconjugated diene monomer at an appropriate temperature, which isgenerally from about −20° C. to about 80° C. In the second stage, theforegoing reaction mixture and the hydrogen phosphite are charged ineither a stepwise or simultaneous manner to the rubber cement containingthe rubbery elastomer and the 1,3-butadiene monomer that is to bepolymerized.

[0107] Fifth, an alternative two-stage procedure may also be employed. Achromium-ligand, molybdenum-ligand, or iron-ligand, complex is firstformed by pre-combining the chromium-containing compound,molybdenum-containing compound, or iron-containing and the hydrogenphosphite compound. Once formed, the chromium complex is then combinedwith the organomagnesium compound, or the molybdenum or iron complex iscombined with the organoaluminum compound, respectively, to form theactive catalyst species. The complex can be formed separately or in therubber cement containing the rubbery elastomer and the 1,3-butadienemonomer that is to be polymerized. This complexation reaction can beconducted at any convenient temperature at normal pressure, butforanincreased rate of reaction, it is preferred to perform this reaction atroom temperature or above. The time required for the formation of thecomplex is usually within the range of about 10 minutes to about 2 hoursafter mixing the chromium-containing, molybdenum-containing oriron-containing compound with the hydrogen phosphite compound. Thetemperature and time used for the formation of the complex will dependupon several variables including the particular starting materials andthe solvent employed. Once formed, the complex can be used withoutisolation from the complexation reaction mixture. If desired, however,the complex may be isolated from the complexation reaction mixturebefore use.

[0108] Sixth, the three catalyst ingredients may be added to the rubbercement prior to or simultaneously with the addition of 1,3-butadienemonomer.

[0109] When a solution of the catalyst composition or one or more of thecatalyst ingredients is prepared outside the polymerization system asset forth in the foregoing methods, an organic solvent or carrier ispreferably employed. Useful organic solvents are described above.Organic solvents may serve to dissolve the catalyst composition oringredients, or the solvent may simply serve as a carrier in which thecatalyst composition or ingredients may be suspended.

[0110] The production of blends of syndiotactic 1,2-polybutadiene andrubbery elastomers according to this invention is accomplished bypolymerizing 1,3-butadiene monomer within the rubber cement by using acatalytically effective amount of at least one of the foregoing catalystcompositions. The total catalyst concentration to be employed in thepolymerization mass depends on the interplay of various factors such asthe purity of the ingredients, the polymerization temperature, thepolymerization rate and conversion desired, and many other factors.Accordingly, a specific total catalyst concentration cannot bedefinitively set forth except to say that catalytically effectiveamounts of the respective catalyst ingredients should be used.Generally, the amount of the chromium-containing, molybdenum-containing,or iron-containing compound used can be varied from about 0.01 to about2 mmol per 100 g of 1,3-butadiene monomer, more preferably from about0.02 to about 1.0 mmol per 100 g of 1,3-butadiene monomer, and even morepreferably from about 0.05 to about 0.5 mmol per 100 g of 1,3-butadienemonomer.

[0111] In performing the polymerization of 1,3-butadiene intosyndiotactic 1,2-polybutadiene within the rubber cement, a molecularweight regulator may be employed to control the molecular weight of thesyndiotactic 1,2-polybutadiene to be produced. As a result, the scope ofthe polymerization system can be expanded in such a manner that it canbe used for the production of syndiotactic 1,2-polybutadiene having awide range of molecular weights. Suitable types of molecular weightregulators that can be utilized include, but are not limited to,α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene,1-heptene, and 1-octene; accumulated diolefins such as allene and1,2-butadiene; nonconjugated diolefins such as 1,6-octadiene,5-methyl-1,4-hexadiene, 1,5-cyclooctadiene, 3,7-dimethyl-1,6-octadiene,1,4-cyclohexadiene, 4-vinylcyclohexene, 1,4-pentadiene, 1,4-hexadiene,1,5-hexadiene, 1,6-heptadiene, 1,2-divinylcyclohexane,5-ethylidene-2-norbornene, 5-methylene-2-norbornene,5-vinyl-2-norbornene, dicyclopentadiene, and 1,2,4-trivinylcyclohexane;acetylenes such as acetylene, methylacetylene and vinylacetylene; andmixtures thereof. The amount of the molecularweight regulator used,expressed in parts per hundred parts by weightof the 1,3-butadienemonomer (phm), is from about 0.01 to about 10 phm, more preferably fromabout 0.02 to about 2 phm, and even more preferably from about 0.05 toabout 1 phm.

[0112] The molecular weight of the syndiotactic 1,2-polybutadiene to beproduced can also be effectively controlled by conducting thepolymerization of 1,3-butadiene monomer in the presence of hydrogen gas.In this case, the partial pressure of hydrogen gas is preferably fromabout 0.01 to about 50 atmospheres.

[0113] The polymerization of 1,3-butadiene into syndiotactic1,2-polybutadiene within the rubber cement may be carried out as a batchprocess, a continuous process, or even a semi-continuous process. In thesemi-continuous process, 1,3-butadiene monomer is intermittently chargedas needed to replace that monomer already polymerized. In any case, thepolymerization is desirably conducted under anaerobic conditions byusing an inert protective gas such as nitrogen, argon or helium, withmoderate to vigorous agitation. The polymerization temperature may varywidely from a low temperature, such as −10° C. or below, to a hightemperature such as 100° C. or above, with a preferred temperature rangebeing from about 20° C. to about 90° C. The heat of polymerization maybe removed by external cooling, cooling by evaporation of the1,3-butadiene monomer or the solvent, or a combination of the twomethods. Although the polymerization pressure employed may vary widely,a preferred pressure range is from about 1 atmosphere to about 10atmospheres.

[0114] Once a desired conversion is achieved, the polymerization of1,3-butadiene monomer into syndiotactic 1,2-polybutadiene within therubber cement can be stopped by adding a polymerization terminator thatinactivates the catalyst system. Typically, the terminator employed toinactivate the catalyst system is a protic compound, which includes, butis not limited to, an alcohol, a carboxylic acid, an inorganic acid,water, or a combination thereof. An antioxidant such as2,6-di-tert-butyl-4-methylphenol may be added along with, before orafter the addition of the terminator. The amount of the antioxidantemployed is usually in the range of 0.2% to 1% by weight of the polymerproduct. When the polymerization reaction has been stopped, the blend ofsyndiotactic 1,2-polybutadiene and the rubbery elastomer can berecovered from the polymerization mixture by utilizing conventionalprocedures of desolventization and drying. For instance, the blend ofsyndiotactic 1,2-polybutadiene and the rubbery elastomer may be isolatedfrom the polymerization mixture by coagulation of the polymerizationmixture with an alcohol such as methanol, ethanol, or isopropanol, or bysteam distillation of the solvent and the unreacted 1,3-butadienemonomer, followed by filtration. The product is then dried to removeresidual amounts of solvent and water. The polymer blend produced is ahighly dispersed blend of crystalline syndiotactc 1,2-polybutadiene inthe rubbery elastomer.

[0115] Advantageously, the catalyst composition employed in thisinvention can be manipulated to vary the characteristics of thesyndiotactic 1,2-polybutadiene in the polymer blend. Namely, thesyndiotactic 1,2-polybutadiene in the polymer blend made by the processof this invention can have various melting temperatures, molecularweights, 1,2-linkage contents, and syndiotacticities, all of which aredependent upon the selection of the catalyst ingredients and theingredient ratios.

[0116] The blends of syndiotactic 1,2-polybutadiene and rubberyelastomers produced with the process of this invention have many uses.For example, these blends can be utilized in rubber compositions thatare used to manufacture the supporting carcass, innerliner, sidewall,and tread of tires. The blends of syndiotactic 1,2-polybutadiene andrubbery elastomers are also useful in the manufacture of films andpackaging materials and in many molding applications.

[0117] In a preferred embodiment, the blend of syndiotactic1,2-polybutadiene in rubbery elastomer is added to rubber compositionsthat are useful in the manufacture of tires. As is generally known inthe art, these rubber compositions or tire formulations include a baserubber, filler, vulcanizing agent, and sundry additional additives thatare common in rubber compounding.

[0118] Both synthetic and natural rubber may be employed within therubber compositions. These rubbers, which may also be referred to aselastomers, include, without limitation, natural rubber, syntheticpolyisoprene, poly(styrene-co butadiene), polybutadiene,poly(styrene-cobutadiene-co-isoprene), poly(styrene-co-isoprene), andmixtures thereof.

[0119] The rubber compositions may include fillers such as inorganic andorganic fillers. Organic fillers include carbon black. Inorganic fillersinclude silica, aluminum hydroxide, magnesium hydroxide, and clays(hydrated aluminum silicates).

[0120] A multitude of rubber vulcanizing agents, which are also referredto as curing agents, can be employed within these rubber compositions.For example, sulfur or peroxide-based curing systems may be employed.Also, see Kirk Othmer, ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY, 3^(rd)Edition, Wiley Interscience, 30 N.Y. 1982, Vol. 20, pp. 365-468,particularly VULCANIZATION AGENTS AND AUXILIARY MATERIALS pp. 390-402,or Vulcanization by A. Y. Coran, ENCYCLOPEDIA OF POLYMER SCIENCE ANDENGINEERING, 2^(nd) Edition, John Wiley & Sons, Inc., 1989, which areincorporated herein by reference. Vulcanizing agents may be used aloneor in combination.

[0121] The rubber compositions may also include other compoundingadditives such as accelerators, oils, waxes, scorch inhibiting agents,processing aids, antidegradants, zinc oxide, optional tackifying resins,optional reinforcing resins, optional fatty acids, and optionalpeptizers.

[0122] In one preferred embodiment, a blend of syndiotactic1,2-polybutadiene and EPDM, prepared according to the process of thisinvention, is employed with a rubber composition that is useful for themanufacture of tire sidewalls. The preferred blend includes from about0.4 to about 12 parts by weight SPB and from about 99.6 to about 88parts by weight EPDM. More preferably, the blend includes from about 2to about 10 parts by weight SPB and from about 98 to about 90 parts byweight EPDM.

[0123] When practicing this embodiment, the blend is combined andcompounded with a base rubber in an amount from about 1 to about 40parts by weight blend phr, preferably from about 2 to about 20 parts byweight phr, and even more preferably from about 5 to about 10 parts byweight blend phr.

[0124] Sidewall formulations also typically include a filler, which isemployed in an amount from about 10 to about 70 parts by weight phr,preferably from 20 about 20 to about 60 parts by weight phr, and morepreferably from about 25 to about 50 parts by weight phr.

[0125] The syndiotactic 1,2-polybutadiene within the EPDM rubberyelastomer that is utilized in tire sidewall formulations preferably hasa melting temperature from about 70 to about 210° C., more preferablyfrom about 90 to about 195° C., and even more preferably from about 110°C. to about 190° C.

[0126] Fillers are typically employed in an amount from about 1 to about100 parts by weight phr, and preferably from about 20 to about 90 partsby weight phr, and more preferably from about 40 to about 80 parts byweight pier.

[0127] Those skilled in the art will be able to choose a useful amountof the other ingredients that may be employed in these rubbercompositions. For example, it is generally known in the art of makingtire components that sulfur is typically employed in an amount fromabout 0.5 to about 10 parts by weight phr, and preferably from about 1to about 6 parts by weight phr. Oils are typically employed in an amountfrom about 1 to about 60 parts by weight phr, and preferably in anamount from about 1 to about 50 parts by weight phr. Zinc oxide istypically employed in an amount from about 0.5 to about 8 by weight phr,and preferably from about 1 to about 5 parts by weight phr.

[0128] Rubber formulations are compounded by using mixing equipment andprocedures conventionally employed in the art. Preferably, an initialmasterbatch is prepared that includes the rubber component and thereinforcing fillers, as well as other optional additives such asprocessing oil and antidegradants. The blend of syndiotactic1,2-polybutadiene and EPDM is preferably added during preparation of theinitial masterbatch. This masterbatch is typically mixed at temperaturesin excess of about 100 or 150° C. To prevent premature vulcanization,also known as scorch, the initial masterbatch generally excludes thevulcanizing agent. Once the initial masterbatch is prepared, thevulcanizing agent is blended into the composition at lower temperatures.Rubber compounding techniques and the additives employed therein aregenerally known as disclosed in The Compounding and Vulcanization ofRubber, by Stevens in RUBBER TECHNOLOGY SECOND EDITION (1973 VanNostrand Reihold Company). The mixing conditions and proceduresapplicable to silica-filled tire formulations are also well known asdescribed in U.S. Pat. Nos. 5,227,425; 5,719,207; 5,717,022, as well asEP 0890606, all of which are incorporated herein by reference.

[0129] The rubber compositions can then be processed into tirecomponents, including sidewalls, according to ordinary tiremanufacturing techniques including standard rubber molding and curingtechniques. Typically, vulcanization is effected by heating thevulcanizable composition in a mold; e.g., it is heated to about 170° C.Cured or crosslinked rubber compositions may be referred to asvulcanizates, which generally contain three-dimensional polymericnetworks that are thermoset. The other ingredients, such as fillers,oils, and antidegradants, are generally dispersed throughout thenetwork.

[0130] While the blends of this invention are preferably added toformulations used to make tire sidewalls, the blend can also be usedwithin other tire components such as treads, subtreads, body ply skims,bead fillers and the like. Pneumatic tires can be made as discussed inU.S. Pat. Nos. 5,866,171; 5,876,527; 5,931,211; and 5,971,046, which areincorporated herein by reference.

[0131] In order to demonstrate the practice of the present invention,the following examples have been prepared and tested as described in theExamples disclosed hereinbelow. The examples should not, however, beconstrued as limiting the scope of the invention. The claims will serveto define the invention.

EXAMPLES Example 1 Preparation of sPB/EPDM Blend

[0132] A highly dispersed blend of syndiotactic 1,2-polybutadiene andEPDM was prepared by polymerizing 1,3-butadiene monomer intosyndiotactic 1,2-polybutadiene within an EPDM rubber cement.

[0133] The EPDM rubber cement was prepared by dissolving 50 g of EPDM toform a solution containing 15% by weight solids by dissolving in 300grams of hexane. The EPDM contained about 56% ethylene, about 6%5-ethylidene-2-norborene, had a number average molecular weight (M_(n))of 60,000 and a Mooney Viscosity (ML₁₊₄@100° C.) of about 35.

[0134] At room temperature, adding 12 grams of a 1,3-butadiene/hexaneblend containing 22.4% by weight of 1,3-butadiene were added to the EPDMrubber cement produced above. The polymerization of the 1,3-butadienemonomer into syndiotactic 1,2-polybutadiene was initiated by theaddition of 6.25 mL of 0.032 M iron (III) 2-ethylhexanoate in hexanes,0.27 mL of 2.93 M bis(2-ethylhexyl) hydrogen phosphite in hexanes, and6.0 mL of 0.68 M triisobutylaluminum in hexanes. The polymerization wasconducted at 50° C. for 6 hours. The polymerization was stopped by theaddition of 3 mL of isopropanol diluted with 50 mL of hexanes. Thepolymerization mixture was added into 10 liters of isopropanolcontaining 12 g of 2,6-di-tert-butyl-4-methylphenol. The polymer blendof 3% syndiotactic 1,2-polybutadiene in EPDM was isolated by filtrationand dried to a constant weight under vacuum of 60° C. Differentialscanning calorimetry (DSC) revealed a broad Tm peak, between 190°-205°C., that was attributed to the formation of syndiotactic1,2-polybutadiene. A blend containing 6% syndiotactic 1,2-polybutadienein EPDM and a blend containing 12% syndiotactic 1,2-polybutadiene inEPDM were prepared exactly as above, except that the amounts of1,3-butadiene monomer and catalyst components were adjusted.

[0135] Analysis showed that SPB did form within the EPDM as evidenced bymelting temperature peaks (Tm) within a DSC curve.

Example 2 Preparation of a 6% sPB/EPDM Blend

[0136] Approximately 50 grams of an EPDM sample (E/P=55/45, M_(n)=60 k,the diene is 5-ethylidene-2-norbornene or ENB, 6%) was dissolved in 450mL of hexanes to form a solution containing 15% solids. A mixture of1,3-butadiene (Bd) monomer in hexanes was charged (5.0 grams total ofBd) followed by the addition of Fe(EHA)₃ (0.1 mmol) in hexanes,HPO(OEH)₂ (0.4 mmol) in hexanes and TIBA (2 mmol) in hexanes. Themixture was agitated at 50° C. for 6 hours. The reaction mixture waspoured into isopropyl alcohol with agitation, isolated, air-dried, andthen vacuum-dried to remove any remaining solvent. The polymer mixturewas analyzed by differential scanning calorimetry (DSC) which revealed abroad T_(m) peak (T_(m)=190-205° C.) attributed to the formation of thesPB.

Examples 3-4 Application of the sPB-EPDM In-Situ Blend In Black SidewallEPDM Formulation

[0137] TABLE 1 Formulations for Examples 3-4 Example 3 4 Formulation PHRPHR JSR EP35* 40 Example 1 blend 40 cis-Polybutadiene 40 40 NaturalRubber 20 20 Carbon Black 50 50 Aromatic Oil 17 17 Stearic Acid 2 2Sulfur 1.5 1.5 Zinc Oxide 3 3 Accelerators Total 0.5 0.5

[0138] *Note: JSR EP35 is an EPDM available from Japan synthetic rubber.TABLE 2 Mixing conditions for Examples 3-4 using a brabender mixer.Master Batch Remill Final Start Temp. ° C. 100 100 70 Dump Temp. ° C.160 160 100 Time (min.) 5 5 2 RPM 60 60 40

[0139] TABLE 3 Properties of Examples 3-4 Stock 3 4 ML 1 + 4 130° C.35.1 38.2 Ring Tensile at 23° C. 622 664 EB % TB 9.27 8.44 M100 1.291.11 Dynastst, Tan Delta at 50° C. 0.194 0.189 Ring Tear at 23° C., EB %578 673 Tear Strength (normalized) 1 1.07

[0140] ML 1+4 130° C. was measured using ASTM-D1646. Ring Tensile at 23°C., EB % was measured using ASTM-D412. Tan Delta at 50° C. was measuredusing a Dynastat Viscosity Analyzer. Ring Tear at 23° C., EB % wasmeasured using ASTM-624. TABLE 4 Cut Growth Rate of Examples 3-4 Stock 34 Crack Growth Resistance 51 45 Dc/Dn (nm/cycle) at 50° C. TearingEnergy (J/m²) 1210 1145

[0141] Dc/Dn (nm/cycle) was measured in a “pure shear” geometry with aprecut [Reference: Lake G J, Rubber Chemistry and Technology, 68: (3),435-460, 1995]. The testing sheet had a length of 20.32 cm, a height of64.5 mm and a thickness of 2 mm. A pre-cut of 4.0 cm was made along thelength direction. Cyclic deformation was applied along the heightdirection with a strain amplitude of 2.5% to 25%, and with a frequencyof 1 to 100 Hz. The testing condition was a 40 Hz half-sinusoidal pulsefor a 5 HZ deformation cycle under 10% strain amplitude at varioustemperatures (23° C.-80° C.). Images of the propagating crack wererecorded automatically at a given interval of about 10,000 cycles. Crackgrowth rate (dc/dn) is then calculated by the increment of crack lengthat each cyde (nm/cycles). This type of cut growth rate of 45 and belowis advantageous in many applications.

[0142] Although the present invention has been described in the aboveexamples with reference to particular means, materials and embodiments,it would be obvious to persons skilled in the art that various changesand modifications may be made, which fall within the scope claimed forthe invention as set out in the appended claims. The invention istherefore not limited to the particulars disclosed and extends to allequivalents within the scope of the claims.

What is claimed is:
 1. A process for preparing blends of syndiotactic1,2-polybutadiene and rubbery elastomers comprising the steps of: (1)providing a mixture of a rubber cement and 1,3-butadiene monomer, wherethe rubber cement comprises an elastomeric terpolymer polymerized fromethylene, at least one α-olefin monomer, and at least one diene monomer;and (2) polymerizing the 1,3-butadiene into syndiotactic1,2-polybutadiene within the rubber cement by using a catalystcomposition that is formed by combining (a) a chromium-containingcompound, (b) a hydrogen phosphite, and (c) an organomagnesium compoundor (a) a molbydenum-containing compound or an iron-containing compound,(b) a hydrogen phosphite, and (c) an organoaluminum compound.
 2. Aprocess for preparing blends of syndiotactic 1,2-polybutadiene andrubbery elastomers comprising the steps of: (1) providing a mixture ofrubber cement and 1,3-butadiene monomer, where the rubber cementcomprises an elastomeric terpolymer polymerized from ethylene, at leastone α-olefin monomer, and at least one diene monomer; and (2) preparinga catalyst composition, where the catalyst composition is prepared bycombining, outside the presence of the mixture of rubber cement andmonomer, (a) a chromium-containing compound, (b) a hydrogen phosphite,and (c) an organomagnesium compound or (a) a molybdenum-containingcompound or an iron-containing compound or (b) a hydrogen phosphite, and(c) an organomagnesium compound; and (3) adding the catalyst compositionto the mixture and thereby polymerizing the 1,3-butadiene monomer intosyndiotactic 1,2-polybutadiene within the rubber cement.
 3. A tiresidewall formulation comprising: a blend of syndiotactic1,2-polybutadiene and rubbery elastomer comprising: an elastomericterpolymer polymerized from ethylene, propylene, and at least one dienemonomer; and syndiotactic 1,2-polybutadiene having a melting temperatureof from about 70° C. to about 210° C.
 4. The process of claim 1, wherethe α-olefin monomer is propylene, 1-butene, 1-hexene, 4-methyl-1pentene, 1-octene, 1-decene, or a combination thereof.
 5. The process ofclaim 1, where the diene monomer is 5-ethylidene-2-norbornene,1,4-hexadiene, 5-methylene-2-norbornene, 1,6-octadiene,5-methyl-1,4-hexadiene, 3,7-methyl-1,6-octadiene, 1,3-cyclopentadiene,1,4-cyclohexadiene, dicyclopentadiene, 5-vinyl-2-norbornene, or acombination thereof.
 6. The process of claim 1, where said step ofcombining (a) a chromium-containing compound, (b) a hydrogen phosphite,and (c) an organomagnesium compound or said step of combining (a) amolybdenum-containing compound, or an iron-containing compound, (b) ahydrogen phosphite, and (c) an organoaluminum compound, occurs in thepresence of at least one type of conjugated diene monomer.
 7. Theprocess of claim 1, where said step of polymerizing includes adding fromabout 0.01 to about 2 mmol of the chromium-containing compound,molybdenum-containing compound, or iron-containing compound per 100 g of1,3-butadiene.
 8. The process of claim 1, where the syndiotactic1,2-polybutadiene has a melting temperature of from about 70° C. toabout 210° C.
 9. The process of claim 1, where the blends ofsyndiotactic 1,2-polybutadiene in rubbery elastomer comprise from about3 percent to about 12 percent by weight of syndiotactic1,2-polybutadiene.
 10. The formulation of claim 3, where thesyndiotactic 1,2-polybutadiene is present in an amount of from about 3to about 12 percent by weight.
 11. A polymer composition comprising ablend of syndiotactic 1,2-polybutadiene and a terpolymer polymerizedfrom ethylene, at least one α-olefin monomer, and at least one dienemonomer.
 12. The polymer composition of claim 11, in which the α-olefinmonomer is propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene,1-decene, or a combination thereof.
 13. The polymer composition of claim11, in which the α-olefin monomer comprises propylene.
 14. The polymercomposition of claim 11, in which the diene monomer comprises5-ethylidene-2-norbornene, 1,4-hexadiene, 5-methylene-2-norbornene,1,6-octadiene, 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene,1,3-cyclopentadiene, 1,4-cyclohexadiene, dicydopentadiene,5-vinyl-2-norbornene, or a combination thereof.
 15. The polymercomposition of claim 11, in which the diene monomer comprises5-ethylidene-2-norbornene.
 16. The polymer composition of claim 11,further comprising cis-polybutadiene.
 17. The polymer composition ofclaim 11, furthercomprising natural rubber.
 18. A method to improve thecut growth rate of a polymer product, comprising combining asyndiotactic 1,2-polybutadiene and a terpolymer polymerized fromethylene, at least one α-olefin monomer, and at least one diene monomer,in the formation of the polymer product.
 19. The method of claim 18wherein the α-olefin monomer comprises propylene, 1-butene, 1-hexene,4-methyl-1-pentene, 1-octene, 1-decene, or a combination thereof. 20.The method of claim 18 wherein the αa-olefin monomer comprisespropylene.
 21. The method of claim 18 wherein the diene monomercomprises5-ethylidene-2-norbornene, 1,4-hexadiene, 5-methylene-2-norbornene,1,6-octadiene, 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene,1,3-cyclopentadiene, 1,4-cyclohexadiene, dicyclopentadiene,5-vinyl-2-norbornene, or a combination thereof.
 22. The method of claim18, further comprising the addition of cis-polybutadiene in theformulation of the polymer product.
 23. The method of claim 18 whereinthe cut growth rate comprises ≧45.